1. Field of the Invention
This invention relates to a pallet exchange apparatus for exchanging the pallets of a machining side and a work exchange side in a machining apparatus such as a machining center.
2. Related Background Art
In a machining apparatus such as a machining center, there is known a pallet exchange apparatus having a pallet on each of a machining side and a work exchange side, and turning and exchanging these pallets by a turn driving apparatus in conformity with the requirement of the machining process. In such a machine, conventionally, a machining side pallet is installed on an XY table freely moved horizontally in the surface direction of that table to thereby effect machining. Heretofore, as the pallet exchange apparatus provided with such turn driving apparatus, there has been an apparatus of a type in which during machining, pallets are fixed so as not to move and during exchange, the pallets are raised by a turning apparatus and thereafter are turned and exchanged by the turn driving apparatus, or an apparatus of a type in which a sliding device such as bearings for exchanging pallets is arranged on not only areas beneath the pallets but also areas below the pallets, and the pallets are moved along the sliding devices and the pallets are exchanged.
Such apparatuses according to the prior art have suffered from the following problems.
(1) Since it is necessary to raise two pallets to be exchanged, a load sufficient to raise the weight of the two pallets has been necessary. To raise and turn the pallets, it is necessary to raise the pallets to a certain degree of height, but a considerably great load has been required to raise the pallets which are weight goods to that position.
(2) Further, oil pressure driving is generally used to raise the pallets, but a great quantity of oil has been required because the quantity to be raised is great.
(3) Since the XY table for machining is moved at random in a horizontal direction during machining, a pallet is disposed at a certain distance from a pallet to be exchanged. Therefore, in the pallet exchange apparatus of the type using the sliding devices such as bearings, it is necessary that the pallet be also moved by the sliding devices over this distance. Thus, the bearings or the like have unavoidably been disposed not only on the lower areas of the pallets but also on the outside areas of the pallets. Therefore, cut powder has been caught into the bearings or the like to hinder smooth movement.
(4) Particularly, the turn driving portion is disposed at a location on which the cut powder always falls, and this has led to the problem that the turn driving portion catches the cut powder into its mechanism.
The present invention provides a pallet exchange apparatus comprising turn driving means rotatable about an axis perpendicular to the plane of a pallet and also movable in the direction of the axis, sliding means disposed only on the lower side of the pallet, and push-up means having sliding means and contacting the sliding means to the pallet being off sliding means, and further guiding the direction of movement of the pallet, and during the exchange of the pallet, the turn driving means turns the pallet on the sliding means and exchanges the pallet, whereby the turning of the pallet can be made possible only by raising the pallet to a slight height and the problem of the load becoming great can be solved. Thereby, further, the quantity of oil may be small in the oil pressure driving for raising the pallet. Also, the necessary load becomes small, whereby it becomes possible to substitute an air oil booster for the oil pressure driving.
The pallet exchange apparatus of the present invention is further characterized in that the sliding means is provided on moving means movable in the direction of the plane of the pallet, and during the exchange of the pallet, the moving means approaches turning means and therefore, the sliding means can be disposed on only the lower side of the pallet. Thereby, the problem that cut powder falls on and is absorbed in the bearings can be solved.
The pallet exchange apparatus of the present invention is further provided with a cover having on the upper portion of the turn driving portion an inclined surface descending from the central portion thereof toward around it, and is characterized in that an insertion bar to transmit rotation force has an inclined surface coinciding with the plane of the cover during descent, and protrudes from the cover during ascent and therefore, the cut powder falling on the turn driving portion does not accumulate but can be dropped. Thereby, the cut powder can be prevented from being absorbed into the turn driving portion and hindering the driving.